Mineral oil composition



Patented June 15, 1943 MINERAL OIL COMPOSITION Robert C. Moran, Wenonah, N. J., Ebenezer E. Reid, Baltimore, Md., and lLyle A. Hamilton, Wenonah, N. .l'., assignors to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a

corporation oi New York No Drawing. Application October 26, 1939, Serial No. 3013M Claims.

This invention has to do with the stabilization of petroleum products such as viscous mineral oil fractions and refined paraflin waxes against the harmful effects of oxidation and deterioration with use. It is more specifically related to the improvement or stabilization of such mineral oil fractions by the use of novel compounds, or a novel class of compounds, which when admixed with a viscous mineral oil in minor proportions will prevent or delay undesirable changes taking place in the oil.

As is well known to those familiar with the art, substantially all the various fractions obtained from mineral oils and refined for their various uses are susceptible to oxidation. This used or tested.

tions, and also upon the conditions of use.

tions.

or of insoluble sludge.

applications of these oils.

ful effects which are undesirable.

tile lubricants and in spray oils.

appreciably accelerated by the presence of metal catalysts such as copper.

Solvent-refined oils in general which have been prepared by treatment with selective solvents, such as chlorex, phenol, iurfural, etc., resemble the moderately refined acid-treated oils in that the oxidation is accelerated by the presence of metals such as copper and further in that it is attended by substantial color depreciation and sludge formation. Acid formation is usually greater than in the case of moderately acid-refined oils but considerably less than with highly refined oils. Both sludge and acid formation lower their value for many purposes such as elec- Also, solvent- The same inhibitor trical insulation, lubrication, etc. susceptibility of an oil fraction to oxidation and refined oils refined for use as internal combusthe manner in which oxidation manifests itself tion e g lubricants, under the Conditions Of within the oil varies with the type and degree use encountered in crankcases, develop constituof refinement to which the oil has been subjected ents which are corrosive toward certain hard and with the conditions under which the oil is 2 metal bearing surfaces Such as the Cadmium- I th d th d O 'l 1 d 11 dth lk h'h n 0 er wor s, e pro ucts s1 ver or copperea a oys an e 1 e w 1c formed in an oil fraction as a result of oxidation are sometimes used in these bearin s. and the degree to which they are formed le- It is to be understood that the foregoing classipends upon the extent to which the various unfication of different types of viscous mineral oil stable constituents which may act as oxidation fractions or hydrocarbon Oi s is by no means Cat lysts have been removed by refining operalimiting and that there can exist oils whose refining and blending has been such as to make A highly refined viscous oil, for example, which hem interm i n p p rtie etween heis one that has been refined by treatment with ypes d sc above. Thus, r sp t0 inhibifuming sulfuric acid or other means or combinators y b said depend entirely 0n the yp tions such as A1013. solvents and acids (or with of Oxidation and end products of oxidation of any large quantities of concentrated sulfuric acid) oil, wh in turn depends l e y pon the detends to form relatively large amounts of acidic gree of refining this l has Further, the constituents when subjected to oxidizing condidegree f fin q ir t prod ce thg yp The presence of catalytic materials such of oils varies with the crude source so at any as copper does not appear to appreciably afiect one refining procedure y produce either a the oxidation of highly refined oils and such oils highly refined Oil a moderately refined Oil are less prone to the formation of colored bodies depending on the Crude from Which it is Obtained The formation of di Pennsylvania type oils, for example, require bodies, however, is highly undesirable for most mu h le r fining to pro e h h y fi e oils For example, when than the Coastal type of oils. used as an nsulating or cooling oil in electrical The use of oxidat on inhibitors for the purpose equipment such as transformers or capacitors an of stab1hzmg a (1500115 mmeral Q naction increase in acidic bodies tends to lower the diagamst the deletenous efifectsof Oxldatlol} d15- electric strength of th 11 and has other harmcussed above is well known. Since the action of The acids are these inhibiting materials is apparently catalytic, corrosive to metals and thus reduce the useful the e e e h g z i dlgicult 3 life of the oils as lubricants or for other urand 1S.eY1dent y m Pence o arge .egree poses where they come in contact with metals. 2 ogldlzable gi t 2 Th k a o owmgapar icu ar re mg rea men us, ese acldlc materials ale also lmunous m tex a particular inhibitor or class of inhibitors may be efiective to stabilize a highly refined oil against b Modegatey g f 5 fl 0115 which have acid formation while the same inhibitors or class een re ne y m Wlth only moderate of inhibitors may have no appreciable effect upon amounts of sulfulicacid, 01 other refining agents, acid color or sludge formation in a moderately tend to form relatively small amounts of acidic efined oil and vice versa oxidation products as compared with highly remay or may not be efiective to inhibit t fi f y ra iglaterial C0101 depreeierosive action of a solvent-refined oil toward alloy ion an orm consi era e amounts of sludge I bearing metals. and the changes taking place in these oils are to The present invention is chiefly concerned with viscous hydrocarbon oil fractions of the "highly refined type and has as its primary object the provision of a class of inhibitor compounds which, when blended in small amounts with highly refined oils, will inhibit the natural tendency of such oils to form acidic products under oxidizing conditions. The invention is predicated upon the discovery that the class of hydrocarbon derivatives of the type which may be obtained by reacting an organic compound containing the II C group with a mercaptan under conditions such that water is released and mercaptan residual groups (SR') replace the oxygen in the 0 II C group, are effective inhibitors for highly refined oils.

Typical compounds containing the 0 ll C..

group which may be reacted with mercaptans to obtain the inhibitors contemplated herein are aidehydes, ketones, organic acids and esters, either aliphatic or cyclic (aromatic and alicyclic) and either unsubstituted or substituted with groups such as -NO2, NR"2, Cl, CO- CO-OR" or other desired groups, wherein R" represents a radical selected from the group consisting of alkyl, aryl, alkaryl and aralkyl radicals. We have discovered that three types of organic compounds falling under the foregoing classifications, which type compounds we may call organic mercaptals," organic mercaptols," and "esters of trithio-ortho acids, are effective stabilizers for highly refined viscous petroleum oils. These types of compounds are, in general, prepared by reacting an aldehyde, a ketone or an acid (or ester), respectively, with a mercaptan in the presence of dry HCl gas. (See Posner, Ber. 33, 2987 (1900) and further articles by the same author.) The reactions by which these typical compounds can be obtained are illustrated by the following general examples and equations.

EXAMPLE I.Mercai tals One mol of aldehyde is mixed with 2 mols of mercaptan and the mixture saturated with 1101 gas to complete the reaction. The reaction mixture is washed with water tofree the product from acid and then topped under high vacuum to remove any unreacted aldehyde or mercaptan. Following this procedure, the following compounds have been prepared: 2-ethylhexaldehyde dibenzyl mercaptal; tolualdehyde dibenzyl mercaptal; benzaldehyde diamyl mercaptal; m-nitro benzaldehyde diamyl mercaptal; formaldehyde diphenyl mercaptal; and formaldehyde ditolyl mercaptal.

The reaction taking place in the procedure may be illustrated by the following equation:

a a sa' (Aldchydcflmermptan) (mercaptal) EXAMPLE II.--Mercaptols The mercaptols may be prepared by following a procedure similar to that described in Example I, using 1 mol of a ketone instead of the alde yde.

Following this procedure we have prepared acetone dibenzyl mercaptol; acetophenone dibenzyl mercaptol; benzophenone dibenzyl mercaptol;

mesityl oxide dibenzyl mercaptol; m-nitro aceto- By using 1 mol of a diketone and 4 mols of mercaptan we have prepared acetyl acetone tetra-amyl mercaptol and acetonyl acetone tetra-phenyl mercaptol. This reaction and the general formula for the product are illustrated in the following equation:

m R(IJSR (Diketonc) (mercaptan) (tetra-mercaptan in which R' is a bivalent hydrocarbon radical.

EXAMPLE III-Esters of trithz'o-ortho acids These compounds are prepared by reacting 3 mols of a mercaptan with 1 mol of an organic acid or ester, following the general procedure described abov under Example 1. Using formic acid and 3 mols of ethyl mercaptan, trithioethyl formate /S.C:H5 HCS.C:H$

S.C1H5

was obtained. The reaction is illustrated by the following equation:

l) HC +3R'SH -o H-CSR' (Formic acid) (mercaptan) (esters of trithioortho formate) Using a formic ester the following reaction takes place:

0 S R D H-C +3RSH HC-SR+ROH+H2O O R S R (F ormic ester) (mercaptan) (esters of trithlo- (alcohol) ortho formate) In the foregoing equations and the formulae therein, R and R represent organic radicals selected from the group consisting of the hydrocarbon radicals, alkyl, aryl, alkaryl, and aralkyl radicals, and substituted hydrocarbon radicals containing substituents from the group consisting of: --NO2,'N'H2, -NR"2, -Cl, -COR", and CO-OR", in which R" represents hydrocarbon radicals from the group consisting of alkyl, aryl, alkaryl and aralkyl radicals.

It will be observed from the products in equations A to D inclusive that the compounds contemplated herein as mineral oil inhibitors are characterized by the presence of at least one carbon atom to which at least two mercaptan resid ual groups (SR') are attached. This general class or group of, compounds may be included under the general formula R(SR')n, in which: R and R are as defined above; n is a whole number from two to four, there being at least two SR groups attached to one carbon atom of the radical R.

The preferred procedure for synthesizing the compounds contemplated herein may be illustrated by the preparation of 2-ethy1hexaldehyde dibenzyl mercaptal, which was prepared by adding 24.8 partsby weight of benzyl mercaptan to 12.8 parts by weight of Z-ethylhexaldehyde. The mixture was cooled in an ice bath and saturated with dry HCl gas. After standing over night two layers formed, and both layers were poured into water and extracted with petroleum ether. The petroleum ether extract was washed with water, dried over anhydrous sodium sulfate, filtered, and the petroleum ether removed on a steam bath. The product was then topped at 2 mm. pressure to a pot temperature of 100 C.

Although the foregoing represents a preferred procedure for obtainig th majority of the compounds contemplated herein, it is to be understood that other methods may be followed. For example, benzaldehyde-di(l-aminophenyl) mercaptal was prepared according to the directions outlined by W. R. Waldron and E. E. Reid, J. A. C. S. 45, 2399 (1923), by reacting one mol of benzal chloride with two mols of the sodium salt of -nitro-thio phenol, and then reducing the benzaldehyde-di(nitrophenyl) mercaptal with iron and acetic acid to obtain the amino derivative which has the formula:

The compounds contemplated herein are both cheap and easy to prepare and they are uniformly very effective in small amounts to inhibit the deteriorating efiec'ts of oxidation on highly refined oils Although these compounds, except perhaps for a few isolated examples, do not appear to be of outstanding eflect iveness as inhibitors for moderately refined and solventrefined oil (for which reason the preferred mineral oil compositions contemplated herein are blends of highly refined oils), it is to be understood that our invention in its broadest aspect contemplates any mineral oil composition in which improvement has been effected by the ad dition thereto of one of the compounds falling within the broad class described herein.

To demonstrate the effectiveness of the compounds contemplated herein as inhibitors for highly refined oils, oil blends were prepared containing small quantities of representative compounds, such blends being subjected to a modified German tar test, which involved heating the oil samples to a temperature of 120 C. and bubbling oxygen gas therethrough for 70 hours, after which the neutralization number (N. N.) of the sample was obtained as an indication of acid formation therein. The oil used in this test was of the type 'used in transformers, obtained from a Coastal distillate and refined by treating first with 40 pounds per barrel of 98 per cent sulfuric acid, followed by 80 pounds per barrel of 103 per cent oleum and neutralization, washing and clay percolation. The finished oil had a specific gravity of 0.871, a flash point of 310 F. and a Saybolt viscosity of 69 seconds at 100 F. The

results of these tests are tabulated in Table I below.

' Table I Inhibitor in sample As we have previously indicated, the present invention is also concerned with the inhibition of acid formation in refined paraflin wax. To demonstrate the eflicacy of the compounds contemplated herein for this purpose, blends containing representative compounds were prepared with a refined parafin wax of 126 F. melting point, and such blends were tested by heating to C. for 70 hours with oxygen gas bubbling therethrough and then determining the neutralization number (N. N.) of the sample. The results obtained, which are set forth in Table 11 below, show that these compounds are effective inhibitors of acid formation in paraffin wax.

It will be seen from the foregoing table that the compounds contemplated herein are highly effective inhibitors of acid formation in highly refined oil and refined paraffin wax. Compound No. 5 (Table I) was only slightly soluble, but in this regard it is to be understood that our invention contemplates the use of suitable solvents, which may be aromatic hydrocarbons such as benzene, toluene, etc., ketones such as-acetone, di-iso-butyl ketone, etc.; alcohols such as methyl, amyl, etc; and esters such as ethyl acetate, etc., to facilitate blending of the less soluble compounds. These compounds may be used in amounts ranging from .01 per cent to 1.0 per cent, but in general it appears that the desired degree of inhibition is obtained with amounts in the neighborhood of 0.10 per cent.

It is to be understood that while we have described one preferred procedure for synthesizing the compounds contemplated herein, the invention is not confined to any particular method of preparing these compounds; also that the term highly refined oil as used herein is not restricted to oil prepared by a particular refining process but is intended rather to indicat oils having inhibitor response similar in general to the oil used in the tested examples. In this regard it is again pointed out that the final properties and characteristics of an oil are derived from the crude oil source as well as the refining treatment, it being possible to obtain a highly refined oil from one crude, by a refining treatment which would yield a moderately refined oil with another crude. The invention, therefore, is not restricted to the specific procedures, compounds, or oils described hereinabove but includes within its scope whatever changes or modificatlons fairly come within the spirit of the appended claims.

We claim:

1. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined parafiin wax and in admixture therewith a minor proportion, from about 0.01 per cent to about 1.0 per cent, of a mercaptal, the said mercaptal being an organic sulfur-containing compound which is characterized by attach ment of two sulfur atoms to a common carbon atom, said common carbon atom also being attached to a hydrogen atom and to a hydrocarbon radical, and the said compound being further characterized by attachment of each of said sulfur atoms to a hydrocarbon radical, and being free of sulfur-containing heterocyclic rings.

2. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of a highly refined viscous mineral oils and refined parafiin wax and in admixture therewith a minor proportion, from about 0.01 percent to about 1.0 per cent, of a mercaptol, the said mercaptol being an organic sulfur-containing compound which is characterized by attachment of two sulfur atoms to a common carbon atom, said common carbon atom also being attached to two hydrocarbon radicals, and said compound being further characterized by attachment of each of said sulfur atoms to a hydrocarbon radical, and being free of sulfur-containing heterocyclic rings.

3. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined paraffin wax and in admixture therewith a minor proportion, from about 0.01 per cent to about 1.0 per cent, of a trithio ester of an ortho acid, said trithio ester being an organic sulfur-containing compound which is characterized by attachment of three sulfur atoms to a common carbon atom and is further characterized by attachment of each of said sulfur atoms to'a hydrocarbon radical, and said trithio ester being free of sulfur-containin heterocyclic rings.

4. An improvedpetroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined parafiin wax and in admixture therewith a minor proportion of a mercaptal, the said mercaptal being an organic sulfur-containing compound which is characterized by attachment of two sulfur atoms to a common carbon atom, said common carbon atom also being attached to a hydrogen atom and to a hydrocarbon radical, and the said compound being further characterized by attachment of each of said sulfur atoms to a hydrocarbon radical, and being free of sulfur-containing heterocyclic rings.

5. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined paraflin wax and in admixture therewith a minor proportion of a mercaptol, the said mercaptol being an organic sulfur-containing compound which is characterized by attachment of two sulfur atoms to a common carbon atom, said common carbon atom also being attached to two hydrocarbon radicals, and said compound being further characterized by attachment of each of said sulfur atoms to a hydrocarbon radical, and being free of sulfur-containing heterocyclic rings.

6. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined paraflin wax and in admixture therewith a minor proportion of a trithio ester of an ortho acid, said trithio esterb'eing an organic sulfur-containing compound which is characterized by attachment of three sulfur atoms to a common carbon atom and is further characterized by attachment of each of said sulfur atoms to a hydrocarbon radical, and said trithio ester being free of sulfur-containing heterocyclic rings.

7. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined parafiin wax and in admixture therewith a minor proportion of a benzaldehyde diamyl mercaptal.

8. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined parafiin wax and in admixtnre therewith a minor proportion of an acetone dibenzyl mercaptol.

9. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined parafiin wax and in admixture therewith a minor proportion of a trithio ethyl ortho formate.

10. An improved petroleum product comprising a mineral oil fraction selected from the group consisting of highly refined viscous mineral oils and refined paraffin wax and in admixture therewith a minor proportion of a compound selected from the group of compounds consisting of mercaptals, mercaptols and trithio esters of ortho acids, which compound is characterized by attachment of at, least two and not more than three sulfur atoms to a common carbon atom and is further characterized by attachment of each of said sulfur atoms to an organic radical selected from the group consisting of hydrocarbon radicals and substituted hydrocarbon radicals containing substituents from the group consisting of -NO2, -NH2, -COR" and COOR" wherein R" represents a hydrocarbon radical, said compound being free of sulfur-containing heterocyclic rings.

ROBERT C. MORAN. EBENEZER E. REID. LYLE A. HAMILTON. 

